The invention relates generally to towed body systems such as those equipped with onboard sensors capable of sensing parameters of an underwater area, and more particularly to a method of controlling the lateral motion and position of such towed bodies.
Underwater searches and surveys are typically carried out by towing a sensor platform through the water. Many underwater sensors have a relatively small range and field-of-view. Consequently, a towed sensor platform carrying one or more sensors must be positioned almost exactly over a target or object of interest, hereinafter referred to simply as the xe2x80x9ctargetxe2x80x9d.
Generally, a target""s location is not known precisely. Therefore, it may not possible to plan a tow track that passes precisely over a target. Furthermore, the towed body""s motion can be disrupted by water currents and wave action. In an attempt to address this problem, towed systems may have a forward-looking sonar that helps to reacquire the target shortly before reaching it. However, the range of the forward-looking sonar is limited. Thus, the advance time provided by the sonar detection is often too short to maneuver the entire system (i.e., the tow craft and towed body sensor platform) to assure that the sensing instrument passes over the target. If the target is missed (i.e., the target does not fall within the towed sensor(s) field-of-view), the entire maneuver must be repeated. This can be very time-consuming, depending on the system, the length of the tow cable, and the sea state conditions.
Accordingly, it is an object of the present invention to provide a method of controlling the lateral position of a body as it is towed through the water.
Another object of the present invention is to provide a method of quickly effecting lateral movement of a body as it is towed through the water.
Still another object of the present invention is to provide a method of controlling the lateral movement of a towed body equipped to effect aileron, elevator and rudder control.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a method of controlling the lateral position of a towed body in water where the body is equipped with effectors for effecting aileron, elevator and rudder control. The body is pulled through the water along a known direction of travel and in a defined frame of reference having one axis along the known direction of travel. A lateral correction is defined by a distance measured perpendicular to the one axis in the frame of reference. A first command indicative of an aileron control is determined that would cause the effectors to move the body laterally of the direction of travel by an amount equal to the lateral correction. A second command indicative of a rudder control is determined that would cause the effectors to move the body laterally of the direction of travel by an amount equal to the lateral correction. The first and second commands are combined to define a combined command that is applied to the effectors so that the optimum aileron and rudder controls are implemented simultaneously.